Where are the button shells?

Last Thursday, most sand stars (Astropecten sp.) went missing at Changi shores. Many hypotheses were made and one of which is their food might be not around, thus explaining their absence. On Saturday, Mei lin smsed me that the Creative Kids group found about 10 sand stars and Chay Hoon found many sand stars too yesterday during their Chek Jawa guided walk.

I'm quite convinced that the sand stars are still around, but I believe in lower numbers and it might be due to the absence of button shells (Umbonium vestiarium), the food for the sand stars. I could not find any button shells at Changi last Thursday.

Thus I've decided to check out Chek Jawa with Yikang this morning to look for the button shells since Chek Jawa, as I what know, has the most extensive button shell beds in Singapore.


With the help of Adelle from Nparks, Yikang and I got a ride from the volunteer hub to Chek Jawa. At first entrance of the place, after three months since I last visited, I felt like homecoming. However, the weather did not look too good. Thank God He sustained the clouds and held the rain till we ended the trip and were back to the volunteer hub.


With the aid of GPS points made during our previous surveys, I went back to different exact plots where plentiful of button shells can be found. Berry and Zamri (1983) stated that button shells can be found hidden 0.5cm-1.5cm deep in clean sand, which is true based on my previous experiences. However, I could not find any plots like that at all today! So I dug very much deeper and saw many whitish shells. It was a tiring digging morning to check them out.


Some white shells looks quite indistinguishable of what it belongs to.


But a closer look shows that they are actually button shells.


But they are all dead.

It's not a mass mortality event caused by lowered salinity. It seems to match in line with my hypothesis stated in my God's wonderful creation blog.

According to Berry and Zamri (1983), it was stated that "progression of this cohort (of button shells) indicated that young settling in May-June grew to full size (11-13mm diameter) by January-March the following year and that virtually all died during their second year, presumably having spawned in March-May". This paper also stated "the older cohort were always more abundant upshore than downshore except in May 1982".

Does this explains the absence or death of button shells in May?


There are still some intact shells left but please do not take these shells away though the snail already died. That is because hermit crabs can also make use of the empty shell to reside in it like this one.


I am still relieved to see several sand stars around. We measured twenty over of them today. Wonder if they can survive without button shells for long. They do also feed on detritus.


These sea stars are quite easily spotted when we reached at 8am. But after 9am, it was difficult to find them! They burrow into the sand like the one on the right. This is because these stars have a circadian rhythm which I will study also soon.

That's about all for the button shells and sand stars observations. Meanwhile, other animals were found as well during our working time.


It's always heartening to see new life on the shore. The noble volute is laying eggs on the sand bar. Soon, we shall have many baby ones.


Like Changi, geographical sea hares can be found.


Yikang spotted for his first time an octopus while I was checking on my anemones.


He also chanced upon this brittlestar that is rather large in my opinion.


I'm glad to see the sandfish sea cucumbers still around. I accidentally stepped onto one since they burrowed and I couldn't see them while walking till suddenly a squirt of water flew up. Haha.


The Nparks volunteers found yet another sea cucumber.


This is not a sea cucumber but a peanut worm. My first time seeing it! Wow, Chek Jawa always reveal surprises with every visit. I never get bored with Chek Jawa. This used to be so common in the past that they take them for feeding worms.


I moved down southwards and check out the guided walk. Everyone was enjoying the session.


It's always good to restrict visitors to just the sand bar while hunter seekers bring the animals to a centralized location. Or else, Chek Jawa might be just trampled to death, or loved to death.


Low tide also means feeding time for shore birds!


I overturned rocks near the boardwalk area while approaching back to House no. 1 and found this hoof-shield limpet (Scutus sp.) like the one we found at Changi last week. Cool!


There is a Bailer volute (Melo melo) at the rescue tank of House no. 1. Wow, I've never seen it before and I wonder where it came from.


At the same time, I got my first hand experience to see the fascinating and magnificient mural done during the May Day Outreach.


House no. 1 was also airing the Remember Chek Jawa film as well.


Before leaving, a hornbill was spotted, though this was the only shot I got before it decided to fly away. Hehe.


Wow, what a great day. The rain poured like nobody's business while we were back at the jetty area. We had a good time chatting and refilling ourselves with 100 plus till the rain stopped. The sky cleared up and I took a photo of Pulau Sekudu with a mountain at Johor on the way back. Nice to also get to know some Ubin volunteers today too. Thanks Yikang for coming to help as well.

I have YET cover everything today in this single post. A trip to Chek Jawa after three months means I have to check out also the other groups of marine animals that we used to monitor. The last monitoring session was at January 2008! About four months ago and it has been some time we monitored or checked them already.

If you want to know how the other groups of animals (except button shells and sand stars discussed in this post) fare now, look out for an upcoming post on their progress.

Reference:
Berry, A.J. and Zamri bin Othman (1983). An annual cycle of recruitment, growth and production in a Malaysian population of the trochacean gastropod Umbonium vestiarium (L.). Estuarine, Coastal and Shelf Science 17: 357–363.

Talk at NUS Faculty of Science Open House

Dear all, I will be sharing with prospective students during NUS Science Open House on Sat 24/5/08 regarding my experience in doing a research project on Chek Jawa. Feel free to come and listen. :-)


Date: 24 May 2008

Location: LT27

Talk Title: Life and death at Chek Jawa. A UROPs research experience in Life Sciences

Talk duration: 15 min (between 2:00-3:30pm)

Speaker name: Mr. LOH Kok Sheng

Speaker profile:

Mr. Loh graduated from Serangoon Junior College and joined NUS in 2005, majoring in life Sciences with specialization in Biology. In July 2007, he received the MOE Teaching Award. Mr. Loh has great interests in ecological work and did an UROPS project under the supervision of N. Sivasothi, Peter Todd and Dan Rittschof. His project aimed to study the mass mortality and recruitment of macrofauna at Chek Jawa in Pulau Ubin. Since the project has application value in understanding and conserving the Singapore macrofauna at Chek Jawa, Mr. Loh’s achievement has been featured in Embracing passion, NUS Advertorial and The Straits Time (March 25 2008). In this talk, Mr. Loh will share with the audience his experience in project work (UROPS) in Life Sciences and highlight those qualities that he has developed through this project as a junior scientist.

More about the Open House: http://www.science.nus.edu.sg/openhouse/index.htm

Anecdotal observations of stress recently

On 12 April 2008, a group of volunteers from Team Seagrass and Chek Jawa guides were out at Chek Jawa. There were some blog postings reported about some signs of unhealthy animals especially for sea stars and a few carpet anemones. Below are a compilation of their observations from various blog posts. All photos and commentary credit to the author of that particular post.

1. Ria Tan's Wildfilm blog: Chek Jawa with TeamSeagrass

"Also rather disturbing, I encountered TWO Biscuit sea stars (Goniodiscaster scabra) that looked like they were unwell. Here's the underside of the first one. The tip of the arm looks more like it's disintegrating rather than having been chomped on by a predator."

"Here's the upperside of the same sea star."

"Nearby, I found another sea star with similar injuries. Oh dear. The last time sea stars disintegrated when there was massive flooding in Johor in early 2007, resulting in a drop in salinity at Chek Jawa. This badly affected some of the marinelife there, especially the sea stars and carpet anemones. And it has been raining quite a bit recently..."

2. Sam Yeo's Ramblings of a Peculiar Nature blog: Back to Chek Jawa: Sat, 12 March 2008

"Found this dead biscuit star under the boardwalk. It looked like it imploded and something that happened to many of the sea creatures during the mass death of Chek Jawa in 2007. Could it be due to the rain of recent days?"

3. Ron Yeo's The Tide Chaser blog: Chek Jawa Walk on 12 Apr 2008


"Some sandstars don't look that healthy though. I found at least 2 more sandstars, which look like they were disintegrating, and part of their body were turning white in colour."

"We also saw a few overturned carpet anemones, and placed them in little tidal pools."

"This poor sea cucumber also looks like it's slowly rotting.The last time we witness all the above phenomenon was during last year's flood, which brought a lot of fresh water into Chek Jawa and many animals die! That certainly got me a little worried, since we have been experiencing heavy rainfall for the past few days."

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According to my study, three areas were hypothesized to cause hyposalinity at Chek Jawa.

1. Increase in discharge of freshwater output from Johor River
2. Direct rainfall

3. Incidence of low tides when point 1 and/or 2 is occuring

Due to the Johor river water level website that is inaccessible at the moment, I can't comment on point 1. Neither do I purchase the rainfall data every month for point 2. But it is true that recently there was quite a number of heavy rain events over the week which coincidented with the low spring tides that started on Monday (7th April 2008) till Sunday (13th April 2008). Though the low tide series is well recorded in the Singapore Tide Tables Year 2008, quantitative data is needed for the rainfall, preferably from Pulau Tekong station.

Echinoderms are stenohaline (unable to withstand wide variation in salinity of surrounding water) in nature and therefore it is not a surprise to see them disintegrating when salinity is lowered beyond a certain limit, which the latter needs to be verified. Anemones like carpet anemones also respond to extreme lowering of salinity. Below is a flow chart of the effects of hyposalinity.

It is yet heartening on another side that the health of Chek Jawa is being looked after and checked by shore volunteers.

Reference

Engebretson, H and Martin, KLM (1994). “Effects of decreased salinity on expulsion of zooxanthellae in the symbiotic sea anemone Anthopleura elegantissima.” Pacific Science, Vol. 48, no. 4, pp. 446-457

Grain size distribution analysis at Chek Jawa

Remember the post made in February regarding Studying substrate variability in Chek Jawa by GIS? It is a team effort made by Yikang, Yong Jian and Jing Kai from NUS Geography department. They went out in February to collect sediments from the transects my project was doing. More about their adventures in my CJ project blog and Ria's wildfilms blog.

The team has done up a website: http://www.rainmuse.com/chekjawa/ where you can conveniently have access to their work. It's interactive, informative and beautiful! Here's some screenshots from the webpage.


The homepage of the website shows the grain size distribution using a Google Map. It was done using GIS applications on the sediment data collected from the transect. I like how you can click on the right side the different sediment size classes and the distribution will be shown on the Google Earth image. Try exploring around to find out more.


You can get to know more about their background, study area, sorting of sediments and most importantly the objectives. To summarise, the main objective will be to gain an insight into the coastal processes affecting the beach at Chek Jawa, in particular the grain size sorting process and the variables that influence this phenomenon. Importantly, this project aims to show that GIS aids in data collection, visualization and manipulation.


If you are curious how they conducted their study, feel free to read more about their sampling, sieving and interpolation method. I believe you will be amazed how technology can aid in research, especially in the area of GIS, which in this project can help to do interpolations of grain distribution in Chek Jawa.


Analysis of results mainly show:

1. Velocity of less than 0.5 m/sec in this area (Wong, 1985) may prove to be significant as from the Hjulstrom curve would imply sediments between 0.01 mm and 0.15 mm may be affected due to sufficient energy of the tidal streams

2. Presence of river indicates source of sediments as well as a counteracting force to the long shore current

3. The sand bar may be the resultant feature of the tidal flow and the river flow due to the lowering of energy levels

4. Selective sorting may also have taken place as can be seen from the progressive reduction in grain sizes further away from the river where fluvial influence is the greatest (Self, 1977)


The last segment explains more about GIS, their limitations, and conclusion.

The team ended off with "This case can serve as a starting point which can be expanded to the other beaches in Singapore, especially in context of the heavy modifications to the coastline in recent years. Knowing how sand grains are sorted can possibly give an idea of the energy level of a particular beach environment (Nordstrom, 1977). This will have implications on the methods of beach protection employed. For instance, predicting the possible morphological changes to the beach should beach nourishment activities take place will help in determining the effectiveness of the activities."

Find out more about their work here: http://www.rainmuse.com/chekjawa/

a big THANK YOU

Monday was the day where my report had to be submitted to the Department office by hook or by crook. Somehow having a dateline is a good thing. It compells me to tighten up my analysis and my writeup, polish it and get ready to present as an end-result. It was a huge struggle trying to complete the report. I'll probably debrief about my project experiences another time. But I want to take this opportunity to thank those who have made my project possible. My vocab and english is not so powerful, so please don't feel offended if I didnt thank you enough with my words. In my heart I am really grateful.


Firstly, would like to thank my main supervisor, Siva (in orange) and also co-supervisor Dr Dan (with a panama hat).


Another of my co-supervisor is Dr Todd from Marine lab. It was the first time he visited Chek Jawa!

Thank you supervisors for being willing to guide, lead, support and encourage me through various ways. Thanks for the great ideas and also for being there when I felt lost and helpless. I might not be the best researcher but I hope my hardwork will make you all proud of me. I have learnt a lot of skills and experiences under you all. They are really useful and invaluable. Thanks for this great journey.


Though not my supervisor, Ria has been significant in my project. She was the one who introduced me to Siva when I thought of working on the mass death at Chek Jawa. Later, she supported me through various many ways. She is also always available to come down frequently to do the monitoring work and even transect work herself. That's really very impressive! She also provided a lot of photos and anecdotal observations of CJ, updating me whenever Johor floods, bringing food and canned drinks for all the volunteers etc etc etc. Thank you Ria!


Another important group of people that I must thank are every single individual that helped me before at my field trips :-)

I am total amazed at how many people that have helped me before! Without volunteers, I can't possibly do this project. I hope you enjoyed working at Chek Jawa. Thank you everyone who helped me before.

Especially want to thank those who helped me not only once, but twice or more. They are Yijun, Pei Hao, Yuchen, Yujie, Raymond, Siyang, Bingquan, Yilin, Robyn, Robert, Liana, July, Yikang, Khairul, Geraldine, Kian Wah, Shuyi, Gerald, Alex, Sam, Nicholas, Gun Kiat and of course Ron.

Would like to thank Yikang and Siyang extra more for being there even during recce trips where we had to cycle up and down from jetty to CJ. Those were the days. We had to wait for an hour long for the boat. Both of you have really ease my project load a lot. Without partnering help like yours, I would have collapsed working alone. Haha.

I would also like to thank the NUS marine (Angie) and eco lab (Tommy) for the equipments. Especially grateful to Ewen for being there and willing to help me with statistics. Also to thank Prof Matthias Roth, Dr Lim Han She and Prof Wong Poh Poh from Geography Department for all the help with regards to the physical aspect of my project. Thanks Dr Daphne Fautin for your great advice on anemones, Joseph Lai for the GPS points from 2001, Zeehan for the photos from previous transects, Cynthia for sharing your project and ideas on salinity, Siti for giving invaluable help regarding how to design a transect sampling method and many others whom I've forgotten to acknowledge. Thank you Uncle Chu for being at all times to fetch us to and fro at Ubin. Your humility impresses me.

Thank you Nparks for allowing me to work at this great place, Chek Jawa. Thank you Choon Beng and Adelle for bridging help along the way at Ubin. Still remember during the earlier days where Choon Beng has to prepare a bicycle the night before so I can use it early next morning for dawn trips. Thank you NUS for this UROPs opportunity. Thanks for the publicities on my project, it gave me a little fame. More importantly, it gave Chek Jawa more attention, horray!

There's simply too many to thank from a blessed heart. Haha. Sorry if I missed out any. But I must also thank my family for unceasingly helping me prepare for trips in terms of logistics and also washing all the sandy and dirty equipment when I come back.

Last but definitely not the least, thank God for being the provider of everything. Thank you for being so real in this period. You have showered so much blessing onto my project, positioning people to help me, ensuring there is no rain in every monitoring or transect session irregardless if its the monsoon season or not. You are truly wonderful!

I sounded like as if this is really the end. Its NOT. Haha. Should be preparing to submit this for a journal, after examinations. Also, Yikang's substrate studies is still ongoing. Hopefully, some people will continue related works in the future after me. Continue to hear more from this blog.

NUS advertorial featuring my project

The Straits Time, 25 March 2008



Thanks Siva for recommending me to be featured.

Mass death of sea star on Kent beach

Amazing picture of thousands of dead starfish washed up on Kent beach
By VANESSA ALLEN at dailymail.co.uk



For five miles they stretched along the beaches, a gruesome line of dead starfish.

Fishermen and bird-watchers at Pegwell Bay near Sandwich, Kent, discovered a "carpet" of thousands of the creatures lying on the sand just above the water line.

And on the beach at nearby Sandwich Bay, thousands more were photographed by Tony Flashman.

"The dead starfish stretched as far as you could see in both directions," said Mr Flashman, of Kingsdown, Deal.

Environment Agency officials are investigating what could have killed the starfish, which had been feeding on mussel beds.

They do not believe the deaths were linked to the recent storms because they were first reported to them last week.

They have also ruled out pollution or anything to do with climate change as the cause.

The agency said officials would investigate if the starfish were discarded by fishermen after the mussel beds were dredged.

A spokesman said: "Starfish congregate in vast numbers in some areas and feed on shellfish, so if the seabed was dredged then the starfish would inevitably have been caught in huge numbers."

Another theory is that the starfish had run out of mussels to eat and had moved into shallow water in the search for food.

The starfish bodies are not harmful and will probably be eaten by seagulls, the agency said.

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Thanks for Samson's post that alerted me on this similar event to mass death of Chek Jawa, though suspected not to be caused by the recent storms.